A field effect transistor which comprises compound semiconductor may operate as a diode which has a negative resistance.
For example, if Gunn oscillation of several tens of GHz is produced, an amplification output at desired frequency decreases.
If an operation layer is divided into a plurality of cell regions and a drain terminal electrode is also divided into a plurality, each drain terminal electrode will be in the state where load is connected, and thereby it becomes easy to control a negative resistance oscillation between adjacent cell regions.
However, dividing a cell region may cause uneven operation.